Vibratory gyroscope using piezoelectric film

ABSTRACT

A vibrating gyroscope according to this invention includes a ring-shaped vibrating body  11  having a uniform plane, a leg portion  15  flexibly supporting the ring-shaped vibrating body and having a fixed end, a fixed potential electrode  16 , and a plurality of electrodes  13   a   , 13   b, . . . ,    13   f  formed on the plane with a piezoelectric film sandwiched between an upper-layer metallic film and a lower-layer metallic film in a thickness direction thereof. In this case, in a representative example shown in FIG.  1 , when one of driving electrodes  13   a  for exciting a primary vibration of the ring-shaped vibrating body  11  in a vibration mode of cos Nθ is set as a reference driving electrode, the plurality of remaining electrodes  13   b, . . . ,    13   f  are disposed at specific positions. Such disposition allows this vibrating gyroscope to excite a primary vibration in an out-of-plane vibration mode of cos 2θ as well as detect a uniaxial or biaxial angular velocity by adopting a secondary vibration detector in an in-plane vibration mode of cos 3θ.

TECHNICAL FIELD

The present invention relates to a vibrating gyroscope using apiezoelectric film, and more particularly relates to a vibratinggyroscope that is capable of measuring variations in maximally biaxialangular velocity.

BACKGROUND ART

In recent years, vibrating gyroscopes using piezoelectric materials havebeen widely developed. There have been conventionally developed agyroscope as described in Patent Document 1, including a vibrating bodyitself made of such a piezoelectric material. On the other hand, thereis a gyroscope using a piezoelectric film that is formed on a vibratingbody. For example, Patent Document 2 discloses a technique for, using aPZT film as a piezoelectric material, exciting a primary vibration of avibrating body as well as for detecting partial distortion of agyroscope, which is caused by a coriolis force generated when an angularvelocity is applied to the vibrating body.

Reduction in size of a gyroscope itself is also an important issue as awide variety of devices mounted with gyroscopes have been quicklyreduced in size. In order to reduce the size of a gyroscope, significantimprovement is required to accuracy of processing each member of thegyroscope. Desired in the industry are not only simple size reductionbut also further improvement in performance of a gyroscope, namely, inaccuracy of detecting an angular velocity. However, the configuration ofthe gyroscope described in Patent Document 2 does not satisfy the demandover the last few years for reduction in size or improvement inperformance.

In view of the above technical problems, the applicants of the presentinvention propose a technical idea of basically performing all themanufacturing steps in a dry process to realize high processing accuracyas well as to satisfy the demand for high performance as a vibratinggyroscope (Patent Document 3).

In addition to the above technical problems, expectations are beingincreased for a vibrating gyroscope that measures an angular velocity ofmulti rotational axes (Patent Document 4, for example). Nevertheless,satisfactory development has not yet been made to a vibrating gyroscopethat has a simple and useful configuration to realize reduction in size.

Patent Document 1: Japanese Unexamined Patent Publication No. H08-271258

Patent Document 2: Japanese Unexamined Patent Publication No. 2000-9473

Patent Document 3: Japanese Patent Application No. 2008-28835

Patent Document 4: Japanese Patent Application No. 2005-529306

Patent Document 5: Japanese Published Patent Publication No. 2002-509615

Patent Document 6: Japanese Published Patent Publication No. 2002-510398

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

As described above, it is very difficult to achieve reduction in sizeand high processing accuracy in a vibrating gyroscope using apiezoelectric film as well as to satisfy, at the same time, the demandfor improvement in performance of the gyroscope. A gyroscope of a smallsize generally has a problem that, upon application of an angularvelocity to a vibrating body, weakened is a signal to be detected by adetection electrode of the gyroscope. Moreover, the vibrating gyroscopeaccording to Patent Document 4 described above adopts a system ofsubstantially measuring variations in capacitance while being capable ofmeasuring an angular velocity of multi rotational axes. As shown inFIGS. 2 and 3 of Patent Document 4, this vibrating gyroscope has acomplex configuration in which several electrodes are not disposed on avibrating body. Therefore, the technical value will be further increasedif a vibrating gyroscope is capable of also measuring an angularvelocity of multi rotational axes in a simple configuration to realizereduction in size.

Solutions to the Problems

The present invention solves the above technical problems tosignificantly contribute to reduction in size and improvement inperformance of a vibrating gyroscope that uses a piezoelectric film andis capable of measuring an angular velocity of a single or multirotational axes. The inventors studied intensively to obtain aconfiguration for solving the respective technical problems by causingthe piezoelectric film to excite a primary vibration as well as todetect a secondary vibration generated by a coriolis force. Found as aresult is that measurement of angular velocities of a single rotationalaxis as well as of multi rotational axes is enabled by refining thedisposition of respective types of electrodes configured by thepiezoelectric film as well as the configuration for supporting thevibrating body. Furthermore, the inventors found that such dispositionthereof can be achieved by a dry process realizing high processingaccuracy. The present invention was created through such a philosophy.It is noted that, in the present application, an “annular or polygonalvibrating gyroscope” is sometimes simply referred to as a “ring-shapedvibrating gyroscope”.

A vibrating gyroscope according to the present invention includes: aring-shaped vibrating body having a uniform plane; a leg portionflexibly supporting the ring-shaped vibrating body and having a fixedend; a fixed potential electrode; and a plurality of electrodes formedon the plane with a piezoelectric film sandwiched between an upper-layermetallic film and a lower-layer metallic film in a thickness directionthereof. The plurality of electrodes include:

(1) when N is a natural number of 2 or more, a group of drivingelectrodes for exciting a primary vibration of the ring-shaped vibratingbody in a vibration mode of cos Nθ, which are disposed (360/N)° apartfrom each other in a circumferential direction; and

(2) a group of detection electrodes for detecting a secondary vibrationin a vibration mode of cos(N+1)θ generated when an angular velocity isapplied to the ring-shaped vibrating body, and, when one of the drivingelectrodes is set as a reference driving electrode and S=0, 1, . . . , N(hereinafter, always true in this paragraph), the group of detectionelectrodes having an electrode disposed [{360/(N+1)}×S]° apart from thereference driving electrode and/or an electrode disposed[{360/(N+1)}×{S+(½)}]° apart from the reference driving electrode.

Further, each of the driving electrodes is disposed on a first electrodedisposition portion in the plane, and each of the detection electrodesis disposed on a second electrode disposition portion that is notelectrically connected to the first electrode disposition portion andhas a region from an outer peripheral edge of the ring-shaped vibratingbody to a vicinity of the outer peripheral edge and/or a region from aninner peripheral edge thereof to a vicinity of the inner peripheraledge.

In this vibrating gyroscope, since a piezoelectric element is formed asan electrode in the specific region described above on the plane of thering-shaped vibrating body, the piezoelectric element functions as auniaxial angular velocity sensor and is capable of exciting the primaryvibration as well as detecting the secondary vibration. In other words,this vibrating gyroscope is capable of exciting the primary vibration ina vibration mode not on a plane including the piezoelectric element(hereinafter, also referred to as an out-of-plane vibration mode) aswell as of detecting the secondary vibration in a vibration mode in theplane (hereinafter, also referred to as an in-plane vibration mode) onlywith use of the piezoelectric element formed on the plane of thering-shaped vibrating body, with no piezoelectric element being formedon a side surface of the ring-shaped vibrating body. Moreover, as thepiezoelectric element is formed only on the plane of the ring-shapedvibrating body, it is possible to fabricate the electrode and thering-shaped vibrating body with a high degree of accuracy in accordancewith the dry process technique. The term “flexible” is used to mean “soas to allow the vibrating body to vibrate” in the entire invention ofthe present application.

Further, it is recognized as significantly advantageous that, when theabove detection electrodes are referred to as first detection electrodesand detection electrodes configured according to (3) described below areadded as second detection electrodes to the plurality of electrodes ofthe above uniaxial vibrating gyroscope, realized is detection of anangular velocity by adopting a totally biaxial (an X axis and a Y axis,for example) in-plane vibration mode. In this case, the detectionelectrodes configured according to (4) are disposed on the secondelectrode disposition portion.

(3) a group of second detection electrodes for detecting a secondaryvibration of a vibration axis {90/(N+1)}° apart from that of thesecondary vibration described in (2), and, when S=0, 1, . . . , N(hereinafter, always true in this paragraph), the group of seconddetection electrodes having an electrode disposed [{360/(N+1)}×{S+(¼)}]°apart from the reference driving electrode and/or an electrode disposed[{360/(N+1)}×{S+(¾)}]° apart from the reference driving electrode.

A different vibrating gyroscope according to the present inventionincludes: a ring-shaped vibrating body having a uniform plane; a legportion flexibly supporting the ring-shaped vibrating body and having afixed end; a fixed potential electrode; and a plurality of electrodesformed on the plane with a piezoelectric film sandwiched between anupper-layer metallic film and a lower-layer metallic film in a thicknessdirection thereof. The plurality of electrodes include:

(1) when N is a natural number of 2 or more, a group of drivingelectrodes for exciting a primary vibration of the ring-shaped vibratingbody in a vibration mode of cos Nθ, which are disposed (360/N)° apartfrom each other in a circumferential direction; and

(2) a group of detection electrodes for detecting a secondary vibrationin a vibration mode of cos(N+1)θ generated when an angular velocity isapplied to the ring-shaped vibrating body, and, when one of the drivingelectrodes is set as a reference driving electrode and S=0, 1, . . . , N(hereinafter, always true in this paragraph), the group of detectionelectrodes having an electrode disposed [{360/(N+1)}×{S+(¼)}]° apartfrom the reference driving electrode and/or an electrode disposed[{360/(N+1)}×{S+(¾)}]° apart from the reference driving electrode.

Further, each of the driving electrodes is disposed on a first electrodedisposition portion in the plane, and each of the detection electrodesis disposed on a second electrode disposition portion that is notelectrically connected to the first electrode disposition portion andhas a region from an outer peripheral edge of the ring-shaped vibratingbody to a vicinity of the outer peripheral edge and/or a region from aninner peripheral edge thereof to a vicinity of the inner peripheraledge.

In this vibrating gyroscope, since a piezoelectric element is formed asan electrode in the specific region described above on the plane of thering-shaped vibrating body, the piezoelectric element functions as auniaxial angular velocity sensor and is capable of exciting the primaryvibration as well as detecting the secondary vibration. In other words,this vibrating gyroscope is capable of exciting the primary vibration inan out-of-plane vibration mode as well as of detecting the secondaryvibration in an in-plane vibration mode only with use of thepiezoelectric element formed on the plane of the ring-shaped vibratingbody, with no piezoelectric element being formed on a side surface ofthe ring-shaped vibrating body. Moreover, as the piezoelectric elementis formed only on the plane of the ring-shaped vibrating body, it ispossible to fabricate the electrode and the ring-shaped vibrating bodywith a high degree of accuracy in accordance with the dry processtechnique.

A different vibrating gyroscope according to the present inventionincludes: a ring-shaped vibrating body having a uniform plane; a legportion flexibly supporting the ring-shaped vibrating body and having afixed end; a fixed potential electrode; and a plurality of electrodesformed on the plane with a piezoelectric film sandwiched between anupper-layer metallic film and a lower-layer metallic film in a thicknessdirection thereof. The plurality of electrodes include:

(1) when N is a natural number of 3 or more, a group of drivingelectrodes for exciting a primary vibration of the ring-shaped vibratingbody in a vibration mode of cos Nθ, which are disposed (360/N)° apartfrom each other in a circumferential direction; and

(2) a group of detection electrodes for detecting a secondary vibrationin a vibration mode of cos(N−1)θ generated when an angular velocity isapplied to the ring-shaped vibrating body, and, when one of the drivingelectrodes is set as a reference driving electrode and S=0, 1, . . . ,N−2 (hereinafter, always true in this paragraph), the group of detectionelectrodes having an electrode disposed [{360/(N−1)}×S]° apart from thereference driving electrode and/or an electrode disposed[{360/(N−1)}×{S+(½)}]° apart from the reference driving electrode.

Each of the driving electrodes is disposed on a first electrodedisposition portion in the plane, and each of the detection electrodesis disposed on a second electrode disposition portion that is notelectrically connected to the first electrode disposition portion andhas a region from an outer peripheral edge of the ring-shaped vibratingbody to a vicinity of the outer peripheral edge and/or a region from aninner peripheral edge thereof to a vicinity of the inner peripheraledge.

In this vibrating gyroscope, since a piezoelectric element is formed asan electrode in the specific region described above on the plane of thering-shaped vibrating body, the piezoelectric element functions as auniaxial angular velocity sensor and is capable of exciting the primaryvibration as well as detecting the secondary vibration. In other words,this vibrating gyroscope is capable of exciting the primary vibration inan out-of-plane vibration mode as well as of detecting the secondaryvibration in an in-plane vibration mode only with use of thepiezoelectric element formed on the plane of the ring-shaped vibratingbody, with no piezoelectric element being formed on a side surface ofthe ring-shaped vibrating body. Moreover, as the piezoelectric elementis formed only on the plane of the ring-shaped vibrating body, it ispossible to fabricate the electrode and the ring-shaped vibrating bodywith a high degree of accuracy in accordance with the dry processtechnique.

Further, it is recognized as significantly advantageous that, when theabove detection electrodes are referred to as first detection electrodesand detection electrodes configured according to (3) described below areadded as second detection electrodes to the plurality of electrodes ofthe above uniaxial vibrating gyroscope, realized is detection of anangular velocity by adopting a totally biaxial (the X axis and the Yaxis, for example) in-plane vibration mode. In this case, the detectionelectrodes configured according to (4) are disposed on the secondelectrode disposition portion.

(3) a group of second detection electrodes for detecting a secondaryvibration of a vibration axis {90/(N−1)}° apart from that of thesecondary vibration described in (2), and, when S=0, 1, . . . , N−2(hereinafter, always true in this paragraph), the group of seconddetection electrodes having an electrode disposed [{360/(N−1)}×{S+(¼)}]°apart from the reference driving electrode and/or an electrode disposed[{360/(N−1)}×{S+(¾)}]° apart from the reference driving electrode.

A different vibrating gyroscope according to the present inventionincludes: a ring-shaped vibrating body having a uniform plane; a legportion flexibly supporting the ring-shaped vibrating body and having afixed end; a fixed potential electrode; and a plurality of electrodesformed on the plane with a piezoelectric film sandwiched between anupper-layer metallic film and a lower-layer metallic film in a thicknessdirection thereof. The plurality of electrodes include:

(1) when N is a natural number of 3 or more, a group of drivingelectrodes for exciting a primary vibration of the ring-shaped vibratingbody in a vibration mode of cos Nθ, which are disposed (360/N)° apartfrom each other in a circumferential direction; and

(2) a group of detection electrodes for detecting a secondary vibrationin a vibration mode of cos(N−1)θ generated when an angular velocity isapplied to the ring-shaped vibrating body, and, when one of the drivingelectrodes is set as a reference driving electrode and S=0, 1, . . . ,N−2 (hereinafter, always true in this paragraph), the group of detectionelectrodes having an electrode disposed [{360/(N−1)}×{S+(¼)}]° apartfrom the reference driving electrode and/or an electrode disposed[{360/(N−1)}×{S+(¾)}]° apart from the reference driving electrode.

Each of the driving electrodes is disposed on a first electrodedisposition portion in the plane, and each of the detection electrodesis disposed on a second electrode disposition portion that is notelectrically connected to the first electrode disposition portion andhas a region from an outer peripheral edge of the ring-shaped vibratingbody to a vicinity of the outer peripheral edge and/or a region from aninner peripheral edge thereof to a vicinity of the inner peripheraledge.

In this vibrating gyroscope, since a piezoelectric element is formed asan electrode in the specific region described above on the plane of thering-shaped vibrating body, the piezoelectric element functions as auniaxial angular velocity sensor and is capable of exciting the primaryvibration as well as detecting the secondary vibration. In other words,this vibrating gyroscope is capable of exciting the primary vibration inan out-of-plane vibration mode as well as of detecting the secondaryvibration in an in-plane vibration mode only with use of thepiezoelectric element formed on the plane of the ring-shaped vibratingbody, with no piezoelectric element being formed on a side surface ofthe ring-shaped vibrating body. Moreover, as the piezoelectric elementis formed only on the plane of the ring-shaped vibrating body, it ispossible to fabricate the electrode and the ring-shaped vibrating bodywith a high degree of accuracy in accordance with the dry processtechnique.

Further, it is a preferable aspect to add monitor electrodes configuredaccording to (4) described below to the plurality of electrodes of anyone of the biaxial vibrating gyroscopes described above, since thedisposition of other electrode groups and/or the metal tracks isfacilitated in a limited planar region of a ring-shaped vibrating bodythat is particularly reduced in size.

(4) when N is a natural number of 2 or more and M=0, 1, . . . , N−1(hereinafter, always true in this paragraph), a group of monitorelectrodes disposed [(360/N)×{M+(½)}]° apart from the reference drivingelectrode in the circumferential direction.

Effects of the Invention

In a vibrating gyroscope according to the present invention, since apiezoelectric element is formed as an electrode in the specific regiondescribed above on the plane of the ring-shaped vibrating body, thepiezoelectric element functions as a uniaxial or biaxial angularvelocity sensor and is capable of exciting the primary vibration as wellas detecting the secondary vibration. In other words, this vibratinggyroscope is capable of exciting the primary vibration in anout-of-plane vibration mode as well as of detecting the secondaryvibration in an in-plane vibration mode only with use of thepiezoelectric element formed on the plane of the ring-shaped vibratingbody, with no piezoelectric element being formed on a side surface ofthe ring-shaped vibrating body. Moreover, as the piezoelectric elementis formed only on the plane of the ring-shaped vibrating body, it ispossible to fabricate the electrode and the ring-shaped vibrating bodywith a high degree of accuracy in accordance with the dry processtechnique.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to an embodiment of thepresent invention.

FIG. 2 is a cross sectional view taken along line A-A of FIG. 1.

FIG. 3A is a cross sectional view showing a process in the steps ofmanufacturing a part of the ring-shaped vibrating gyroscope according tothe embodiment of the present invention.

FIG. 3B is a cross sectional view showing a process in the steps ofmanufacturing the part of the ring-shaped vibrating gyroscope accordingto the embodiment of the present invention.

FIG. 3C is a cross sectional view showing a process in the steps ofmanufacturing the part of the ring-shaped vibrating gyroscope accordingto the embodiment of the present invention.

FIG. 3D is a cross sectional view showing a process in the steps ofmanufacturing the part of the ring-shaped vibrating gyroscope accordingto the embodiment of the present invention.

FIG. 3E is a cross sectional view showing a process in the steps ofmanufacturing the part of the ring-shaped vibrating gyroscope accordingto the embodiment of the present invention.

FIG. 3F is a cross sectional view showing a process in the steps ofmanufacturing the part of the ring-shaped vibrating gyroscope accordingto the embodiment of the present invention.

FIG. 4 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to another embodiment of thepresent invention.

FIG. 5 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to still another embodiment ofthe present invention.

FIG. 6 is a cross sectional view, which corresponds to FIG. 2, of astructure having a principal function in a ring-shaped vibratinggyroscope according to a different embodiment of the present invention.

FIG. 7 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 8 is a cross sectional view taken along line B-B of FIG. 7.

FIG. 9 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 10 is a cross sectional view taken along line C-C of FIG. 9.

FIG. 11A is a view conceptually illustrating a primary vibration in anout-of-plane vibration mode of cos 2θ according to an embodiment of thepresent invention.

FIG. 11B is a view conceptually illustrating a secondary vibration in anin-plane vibration mode of cos 3θ in a case where an angular velocity isapplied about an X axis, according to an embodiment of the presentinvention.

FIG. 11C is a view conceptually illustrating a secondary vibration in anin-plane vibration mode of cos 3θ in a case where an angular velocity isapplied about a Y axis, according to an embodiment of the presentinvention.

FIG. 12A is a view conceptually illustrating a primary vibration in anout-of-plane vibration mode of cos 3θ according to a differentembodiment of the present invention.

FIG. 12B is a view conceptually illustrating a primary vibration in anin-plane vibration mode of cos 2θ in a case where an angular velocity isapplied about an X axis, according to a different embodiment of thepresent invention.

FIG. 12C is a view conceptually illustrating a primary vibration in anin-plane vibration mode of cos 2θ in a case where an angular velocity isapplied about a Y axis, according to a different embodiment of thepresent invention.

FIG. 13 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 14A is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 14B is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 14C is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 14D is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 14E is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

FIG. 14F is a front view of a structure having a principal function in aring-shaped vibrating gyroscope according to a different embodiment ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described in detail withreference to the accompanying drawings. In the description, common partsare denoted by common reference symbols in all the drawings unlessotherwise specified. Further, the elements in these embodiments are notnecessarily illustrated in accordance with the same scale.

First Embodiment

FIG. 1 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope 100 for measuring a biaxial angularvelocity according to the present embodiment. FIG. 2 is a crosssectional view taken along line A-A of FIG. 1. For the purpose of easierillustration, an X axis and a Y axis are indicated in FIG. 1.

As shown in FIGS. 1 and 2, the ring-shaped vibrating gyroscope 100according to the present embodiment is generally divided into threestructures. A first structure includes a ring-shaped vibrating body 11formed with a silicon substrate 10, a silicon oxide film 20 on an upperplane (hereinafter, referred to as an upper surface) of the ring-shapedvibrating body 11, and a plurality of electrodes 13 a to 13 f formedthereon with a piezoelectric film 40 sandwiched between a lower-layermetallic film 30 and an upper-layer metallic film 50. In the presentembodiment, the upper-layer metallic film 50 configuring the pluralityof electrodes 13 b to 13 e has an outer end or an inner end formedinside by approximately 1 μm with respect to the outer peripheral edgeor the inner peripheral edge of the ring-shaped vibrating body 11 thathas a ring-shaped plane of approximately 40 μm wide, so as to beapproximately 12 μm wide. In the upper-layer metallic film 50, the fourelectrodes 13 a and 13 f are formed to include a center line so as to beapproximately 12 μm wide. The twelve electrodes are formed outside aline connecting centers (hereinafter, simply referred to as a centerline) of both ends in the width direction of the ring-shaped plane thatserves as the upper surface of the ring-shaped vibrating body 11. Theremaining twelve electrodes are formed inside the center line.

In the present embodiment, a primary vibration of the ring-shapedvibrating gyroscope 100 is excited in an out-of-plane vibration mode ofcos 2θ as shown in FIG. 11A. A secondary vibration in the presentembodiment has an in-plane vibration mode of cos 3θ with respect to theX axis as shown in FIG. 11B and an in-plane vibration mode of cos 3θwith respect to the Y axis as shown in FIG. 11C.

Thus, the plurality of electrodes 13 a to 13 f are categorized asfollows. Firstly, two driving electrodes 13 a, 13 a are disposed 180°apart from each other in a circumferential direction.Alternating-current power supplies to be connected with the drivingelectrodes 13 a, 13 a are not illustrated for the purpose of easiercomprehension of the figure. In a case where one of the above twodriving electrodes 13 a, 13 a (for example, the driving electrode 13 adisposed in the direction of twelve o'clock in FIG. 1) is set as areference electrode, two monitor electrodes 13 f, 13 f are disposed 90°and 270° apart from the driving electrode 13 a in the circumferentialdirection. Assume that the plane of the ring-shaped vibrating body onwhich a piezoelectric element is disposed, in other words, the drawingsheet of FIG. 1, is an X-Y plane. In this case, first detectionelectrodes 13 b, 13 c are disposed 0°, 60°, 120°, 180°, 240°, and 300°apart from the reference electrode in the circumferential direction.Each of the first detection electrodes 13 b, 13 c detects a secondaryvibration generated when an angular velocity about the X axis is appliedto the ring-shaped vibrating gyroscope 100. Similarly, second detectionelectrodes 13 d, 13 e are disposed 30°, 90°, 150°, 210°, 270°, and 330°apart from the reference electrode in the circumferential direction.Each of the second detection electrodes 13 d, 13 e detects a secondaryvibration generated when an angular velocity about the Y axis is appliedto the ring-shaped vibrating gyroscope 100.

In the present embodiment, the lower-layer metallic film 30 and theupper-layer metallic film 50 are 100 nm thick, respectively, and thepiezoelectric film 40 is 3 μm thick. The silicon substrate 10 is 100 μmthick.

In the present embodiment and other embodiments to be described later,there are two categorized portions in which the respective electrodesare disposed. One of the portions is referred to as a second electrodedisposition portion, in which the first detection electrodes 13 b, 13 cand the second detection electrodes 13 d, 13 e are disposed, whichincludes a region from the outer peripheral edge of the upper surface ofthe ring-shaped vibrating body 11 to a vicinity of the outer peripheraledge and/or a region from the inner peripheral edge thereof to avicinity of the inner peripheral edge. Another one of the two portionsis referred to as a first electrode disposition portion, in which therespective driving electrodes 13 a, 13 a are disposed, which is locatedon the upper surface of the ring-shaped vibrating body 11 so as not tobe electrically connected to the second electrode disposition portion.

A second structure includes leg portions 15, . . . , 15 that are eachconnected to a part of the ring-shaped vibrating body 11. These legportions 15, . . . , 15 are also formed with the silicon substrate 10.Formed on the entire upper surfaces of the leg portions 15, . . . , 15are the silicon oxide film 20, the lower-layer metallic film 30, and thepiezoelectric film 40 described above which are provided continuously tothe portions of the respective films on the ring-shaped vibrating body11. Further formed on a center line in the upper surface of thepiezoelectric film 40 is the upper-layer metallic film 50 which servesas metal tracks 14, . . . , 14 of approximately 8 μm wide.

In the present embodiment, the plurality of metal tracks 14 are formedon twelve leg portions 15, . . . , 15 out of twenty four leg portions15, . . . , 15. These metal tracks 14 are formed to obtain paths toelectrode pads 18 on a post 19 from the respective electrodes that aredisposed in the region from the outer peripheral edge of the ring-shapedvibrating body 11 to the vicinity of the outer peripheral edge or aredisposed so as to include the center line. Particularly in the presentembodiment, the metal tracks 14, 14 are provided from both ends of eachof the second detection electrodes 13 d, 13 e so as to eliminatevariations in electrical signals from the second detection electrodes 13d, 13 e. The function of the vibrating gyroscope is not affected even ina case where the metal tracks 14, 14 are provided only from one of theends of the respective second detection electrodes 13 b, 13 d.

A third structure includes the post 19 that is formed with the siliconsubstrate 10 provided continuously to the portions of the above legportions 15, . . . , 15. In the present embodiment, the post 19 isconnected to a package portion (not shown) of the ring-shaped vibratinggyroscope 100 and serves as a fixed end. The post 19 is provided withthe electrode pads 18, . . . , 18. As shown in FIG. 2, formed on theupper surface of the post 19 are the silicon oxide film 20, thelower-layer metallic film 30, and the piezoelectric film 40 describedabove, which are provided continuously to the portions of the respectivefilms on the leg portions 15, . . . , 15 except for the portion of thefixed potential electrode 16 that functions as the ground electrode. Inthis case, the lower-layer metallic film 30 formed on the silicon oxidefilm 20 functions as the fixed potential electrode 16. On the uppersurface of the piezoelectric film 40 formed above the post 19, there areformed the metal tracks 14, . . . , 14 as well as the electrode pads 18,. . . , 18 which are provided continuously to the portions of the metaltracks on the leg portions 15, . . . , 15.

Described next with reference to FIGS. 3A to 3F is a method formanufacturing the ring-shaped vibrating gyroscope 100 according to thepresent embodiment. FIGS. 3A to 3F are cross sectional views eachshowing a part of the portion shown in FIG. 2.

Firstly, as shown in FIG. 3A, laminated on the silicon substrate 10 arethe silicon oxide film 20, the lower-layer metallic film 30, thepiezoelectric film 40, and the upper-layer metallic film 50. Each ofthese films is formed by known film formation means. In the presentembodiment, the silicon oxide film 20 is a thermally oxidized filmobtained by known means. The lower-layer metallic film 30, thepiezoelectric film 40, and the upper-layer metallic film 50 are eachformed in accordance with a known sputtering method. It is noted thatformation of each of these films is not limited to the above example butthese films may be alternatively formed by any other known means.

The upper-layer metallic film 50 is then partially etched. In thepresent embodiment, there is formed a known resist film on theupper-layer metallic film 50, and dry etching is then performed on thebasis of a pattern formed in accordance with the photolithographictechnique, so that formed is the upper-layer metallic film 50 shown inFIG. 3B. In this case, the upper-layer metallic film 50 was dry etchedunder the condition for the known reactive ion etching (RIE) using argon(Ar) or mixed gas containing argon (Ar) and oxygen (O₂).

Thereafter, as shown in FIG. 3C, the piezoelectric film 40 is partiallyetched. Firstly, similarly to the above, the piezoelectric film 40 isdry etched on the basis of the resist film that is patterned inaccordance with the photolithographic technique. In the presentembodiment, the piezoelectric film 40 was dry etched under the conditionfor the known reactive ion etching (RIE) using mixed gas containingargon (Ar) and C₂F₆ gas, or mixed gas containing argon (Ar), C₂F₆ gas,and CHF₃ gas.

Then, as shown in FIG. 3D, the lower-layer metallic film 30 is partiallyetched. In the present embodiment, dry etching is performed using theresist film that is again patterned in accordance with thephotolithographic technique, so as to form the fixed potential electrode16 utilizing the lower-layer metallic film 30. In the presentembodiment, the fixed potential electrode 16 is used as the groundelectrode. In the present embodiment, the lower-layer metallic film 30was dry etched under the condition for the known reactive ion etching(RIE) using argon (Ar) or mixed gas containing argon (Ar) and oxygen(O₂).

In the present embodiment, the resist film is formed to be approximately4 μm thick so that the silicon oxide film 20 and the silicon substrate10 are thereafter continuously etched with the above resist film formedagain serving as an etching mask. However, even in a case where thisresist film disappears during etching the silicon substrate 10, theselectivity of the etching rate relative to an etchant applied to thesilicon substrate 10 functions advantageously. Therefore, theperformance of any one of the upper-layer metallic film 50, thepiezoelectric film 40, and the lower-layer metallic film 30 is notsubstantially affected by the above etching. In other words, in thepresent embodiment, since the ring-shaped vibrating body 11 is formedwith the silicon substrate, it is possible to apply the known silicontrench etching technique with an adequately high selectivity withrespect to the resist film. Even in a case where the resist filmdisappears, there is provided an adequate selectivity such that theupper-layer metallic film or the piezoelectric film provided therebelowserves as a mask for etching silicon.

Thereafter, as shown in FIGS. 3E and 3F, the silicon oxide film 20 andthe silicon substrate 10 are dry etched as described above using theresist film that is provided for etching the lower-layer metallic film30. In the present embodiment, the silicon oxide film 20 was dry etchedunder the condition for the known reactive ion etching (RIE) using argon(Ar) or mixed gas containing argon (Ar) and oxygen (O₂). The knownsilicon trench etching technique is applied to the dry etching of thesilicon substrate 10 in the present embodiment. In this case, thesilicon substrate 10 is etched so as to be penetrated. Thus, the dryetching described above is performed in a state where a protectivesubstrate, which prevents a stage to allow the silicon substrate 10 tobe mounted thereon from being exposed to plasma upon penetration, isattached to the silicon substrate 10 with grease of high thermalconductivity serving as a lower layer of the silicon substrate 10.Accordingly, it is a preferable aspect to adopt the dry etchingtechnique described in Japanese Unexamined Patent Publication No.2002-158214, for example, in order to prevent corrosion of a planeperpendicular to the thickness direction of the silicon substrate 10,that is, an etching side surface, after the penetration.

As described above, the silicon substrate 10 and the respective filmslaminated on the silicon substrate 10 are etched to form the mainstructural portion of the ring-shaped vibrating gyroscope 100.Subsequently performed are the steps of accommodating the mainstructural portion into the package by known means as well as wiring. Asa result, there is formed the ring-shaped vibrating gyroscope 100.Therefore, this vibrating gyroscope 100, which has no piezoelectricelement on a side surface of the ring-shaped vibrating body 11, realizesexcitation of an out-of-plane primary vibration as well as detection ofa maximally biaxial in-plane secondary vibration with use of only thepiezoelectric element formed on the plane of the ring-shaped vibratingbody 11. As a result, it is possible to manufacture the vibratinggyroscope 100 in accordance with the above dry process technique thatrealizes low cost mass production with a high degree of accuracy.

Described below are the functions of the respective electrodes includedin the ring-shaped vibrating gyroscope 100. As already described,excited in the present embodiment is the primary vibration in anout-of-plane vibration mode of cos 2θ. As the lower-layer metallic film30 is formed continuously to the fixed potential electrode 16 beinggrounded, the lower-layer metallic film 30 is uniformly set to 0 V.

Firstly, an alternating-current voltage of 1 VP-0 is applied to each ofthe two driving electrodes 13 a, 13 a. As a result, the piezoelectricfilm 40 is expanded and contracted to excite the primary vibration. Inthe present embodiment, the upper-layer metallic film 50 is formed toinclude the center line of the ring-shaped vibrating body 11 in a frontview. In this state, due to deformation of the piezoelectric film, asecondary vibration in an in-plane vibration mode is unlikely to beexcited. However, the respective driving electrodes 13 a may be disposednot to include the center line as long as the resonance point of theprimary vibration and that of the secondary vibration are different fromeach other in the ring-shaped vibrating body 11.

Then, each of the monitor electrodes 13 f, 13 f shown in FIG. 1 detectsan amplitude and a resonant frequency of the above primary vibration,and transmits a signal to a known feedback control circuit (not shown).The feedback control circuit in the present embodiment controls usingthe signals from the monitor electrodes 13 f, 13 f such that thefrequency of the alternating-current voltage applied to each of thedriving electrodes 13 a, 13 a is equal to the natural frequency of thering-shaped vibrating body 11, as well as such that the amplitude of thering-shaped vibrating body 11 has a constant value. As a result, thering-shaped vibrating body 11 is vibrated constantly and continuously.

Described below is a case where an angular velocity is applied about theX axis after the excitation of the primary vibration described above.Excited in this case is the secondary vibration in the in-planevibration mode of cos 3θ as indicated in FIG. 11B.

This secondary vibration is detected by the six detection electrodes(first detection electrodes) 13 b, . . . , 13 b and the other sixdetection electrodes (first detection electrodes) 13 c, . . . , 13 c. Inthe present embodiment, as shown in FIG. 1, the respective detectionelectrodes 13 b, 13 c are disposed in correspondence with the vibrationaxis of the in-plane secondary vibration. The respective detectionelectrodes 13 b, 13 c in the present embodiment are disposedrespectively outside and inside the center line on the upper surface ofthe ring-shaped vibrating body 11 so as to detect most easily thesecondary vibration to be detected, namely, the vibration in thein-plane vibration mode.

In the present embodiment, because of the disposition of the respectivedetection electrodes 13 b, 13 c, the detection electrodes 13 b, 13 cgenerate electrical signals of positive/negative polarities inverse toeach other in accordance with the in-plane secondary vibration excitedupon application of the angular velocity. Thus obtained in an arithmeticcircuit functioning as a known difference circuit are differencesbetween the electrical signals of the respective detection electrodes 13b, 13 c. Resulting detection signals of this case have approximatelydoubled detectability in comparison to the case with only one kind ofthe detection electrodes.

Described below is a case where an angular velocity is applied about theY axis after the excitation of the primary vibration described above.Excited in this case is the secondary vibration in the in-planevibration mode of cos 3θ as indicated in FIG. 11C.

This secondary vibration is detected by the six detection electrodes(second detection electrodes) 13 d, . . . , 13 d and the other sixdetection electrodes (second detection electrodes) 13 e, . . . , 13 e.In the present embodiment, as shown in FIG. 1, the respective detectionelectrodes 13 d, 13 e are disposed in correspondence with the vibrationaxis of the in-plane secondary vibration. The respective detectionelectrodes 13 d, 13 e in the present embodiment are also disposedrespectively outside and inside the center line on the upper surface ofthe ring-shaped vibrating body 11 so as to detect most easily thesecondary vibration to be detected, namely, the vibration in thein-plane vibration mode.

In the present embodiment, because of the disposition of the respectivedetection electrodes 13 d, 13 e, the detection electrodes 13 d, 13 egenerate electrical signals of positive/negative polarities inverse toeach other in accordance with the in-plane secondary vibration excitedupon application of the angular velocity. Thus, similarly to the abovecase, obtained in the arithmetic circuit functioning as a knowndifference circuit are differences between the electrical signals of therespective detection electrodes 13 d, 13 e. Resulting detection signalsof this case have approximately doubled detectability in comparison tothe case with only one kind of the detection electrodes.

In the first embodiment described above, for the purpose of easierdescription, the detection electrodes are referred to as the firstdetection electrodes and the second detection electrodes, each of whichdetects one axial component of a biaxial angular velocity to bedetected. Alternatively, the detection electrodes for the respectiveaxes may be each arbitrarily referred to as one of the first detectionelectrode and the second detection electrode so as to be different fromeach other.

Modification (1) of First Embodiment

FIG. 4 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope 200 obtained by partially modifying thefirst embodiment.

The ring-shaped vibrating gyroscope 200 according to the presentembodiment is configured identically with the ring-shaped vibratinggyroscope 100 of the first embodiment, except for the upper-layermetallic film 50 in the first embodiment. The manufacturing methodtherefor is identical with that of the first embodiment except for somesteps. The vibration modes of the primary vibration and the secondaryvibration in the present embodiment are identical with those of thefirst embodiment. Accordingly, the description duplicating with that ofthe first embodiment will not be repeatedly provided.

As shown in FIG. 4, the ring-shaped vibrating gyroscope 200 according tothe present embodiment includes four detection electrodes 13 b, 13 c, 13d, 13 e. The effect of the present invention is substantially exertedeven with such disposition of the respective detection electrodes. Morespecifically, provision of the respective detection electrodes 13 b, 13;13 d, 13 e achieves detection of an angular velocity by adopting thebiaxial (the X axis and the Y axis) in-plane vibration mode.Detectability of the present embodiment is not as good as that of thefirst embodiment since there are provided the only four detectionelectrodes 13 b, 13 c, 13 d, 13 e, each of which has an area identicalto the corresponding one of the first embodiment. FIG. 4 alsoillustrates alternating-current power supplies 12, 12, which are notincluded in FIG. 1 for the purpose of easier illustration. The actualalternating-current power supplies 12, 12 each apply to thecorresponding driving electrode 13 a by way of the correspondingelectrode pad 18 that is connected to a conductive wire. However, thealternating-current power supplies 12, 12 are not referred to in thepresent embodiment and in the other embodiments, for the purpose ofeasier description.

As the respective electrodes of the present embodiment are eccentricallylocated, some of the leg portions 15 are not provided with the metaltracks 14. However, the present invention is not limited to such a case.An effect similar to that of the present embodiment is exerted even in acase where the leg portions 15 not provided with the metal tracks 14 areremoved. However, random absence of the leg portions 15 may causeirregular vibration of the ring-shaped vibrating body 11. It istherefore preferable to remove only the leg portions 15 that areallocated at equal angles.

Modification (2) of First Embodiment

FIG. 5 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope 300 obtained by partially modifying thefirst embodiment.

The ring-shaped vibrating gyroscope 300 according to the presentembodiment is configured identically with the ring-shaped vibratinggyroscope 100 of the first embodiment, except for the upper-layermetallic film 50 in the first embodiment. The manufacturing methodtherefor is identical with that of the first embodiment except for somesteps. The vibration modes of the primary vibration and the secondaryvibration in the present embodiment are identical with those of thefirst embodiment. Accordingly, the description duplicating with that ofthe first embodiment will not be repeatedly provided.

As shown in FIG. 5, the ring-shaped vibrating gyroscope 300 according tothe present embodiment is provided only with driving electrodes 13 a, 13a, monitor electrodes 13 f, 13 f, an electrode 13 b as one of firstdetection electrodes used for measuring an angular velocity with respectto an X axis, and an electrode 13 e as one of second detectionelectrodes used for measuring an angular velocity with respect to a Yaxis. A part of each of the driving electrodes 13 a, 13 a is located onthe center line as well as from the center line to a vicinity of theinner peripheral edge. Further, each of the detection electrodes 13 b,13 e has the electrode portion located from the center line to avicinity of the outer peripheral edge or from the center line to avicinity of the inner peripheral edge. Even with such disposition of therespective electrodes, there is exerted an effect substantially similarto that of the first embodiment. More specifically, when there areprovided, out of the detection electrodes of the first embodiment, atleast one of the first detection electrodes 13 b, 13 c for the X axisand at least one of the second detection electrodes 13 d, 13 e for the Yaxis, it is possible to detect an angular velocity by adopting thebiaxial (the X axis and the Y axis) in-plane vibration mode.

The respective driving electrodes 13 a are preferably disposed so as toexcite only the primary vibration in the out-of-plane vibration mode aswell as to be unlikely to excite the secondary vibration in the in-planevibration mode. Such disposition is preferable because generation of thesecondary vibration with no angular velocity being applied causes thering-shaped vibrating gyroscope 300 to generate a zero point output. Inthe in-plane vibration mode, it is a preferable aspect to dispose therespective driving electrodes 13 a so as to include the center line aseach of the driving electrodes is less deformed in a vicinity of thecenter line, which is unlikely to excite the secondary vibration in thein-plane vibration mode. In the in-plane vibration mode, since thedriving electrodes are deformed in directions opposite to each otherwith respect to the center line, it is a more preferable aspect todispose the respective driving electrodes 13 a so as to be symmetricalwith respect to the center line. Even in a case where the plurality ofdriving electrodes 13 a are not disposed symmetrically with respect tothe center line, the respective driving electrodes 13 a may be disposedin various ways so as to be unlikely to excite a vibration in anin-plane vibration mode in accordance with the vibration mode to beadopted. Accordingly, the first electrode disposition portion includingthe respective driving electrodes 13 a is defined as a portion on theupper surface of the ring-shaped vibrating body 11 not electricallyconnected to the second electrode disposition portion.

Each of the detection electrodes 13 b, 13 e has the electrode portiondisposed to include the center line. In this case, the detectionsensitivity for the secondary vibration in the in-plane vibration modeis improved if the electrode portions are located only in a region fromthe outer peripheral edge of the ring-shaped vibrating body 11 to avicinity of the outer peripheral edge and/or only in a region from theinner peripheral edge thereof to a vicinity of the inner peripheraledge. In the in-plane vibration mode, such disposition is preferablebecause the driving electrodes are deformed in directions opposite toeach other with respect to the center line, resulting in that a signaloutputted from the electrode portion crossing the center linedeteriorates the magnitude of the detection signals.

The present embodiment realizes simplification of the circuit as thedifference circuit used in the first embodiment is not required.Further, in the present embodiment, one of the driving electrodes 13 ais formed to have an area larger than that of the first embodiment. Sucha large area of the driving electrode 13 a also saves drivingelectricity.

In the present embodiment, the monitor electrode 13 f has an area equalto that of the first embodiment. However, the present invention is notlimited to such a case. It is a preferable aspect to improve thedetectability by increasing the area of the monitor electrode.

As the respective electrodes of the present embodiment are eccentricallylocated, some of the leg portions 15 are not provided with the metaltracks 14. However, the present invention is not limited to such a case.An effect similar to that of the present embodiment is exerted even in acase where the leg portions 15 not provided with the metal tracks 14 areremoved. However, random absence of the leg portions 15 may causeirregular vibration of the ring-shaped vibrating body 11. It istherefore preferable to remove only the leg portions 15 that areallocated at equal angles.

Modification (3) of First Embodiment

FIG. 6 is a cross sectional view, which corresponds to FIG. 2, of astructure having a principal function in a ring-shaped vibratinggyroscope 400 obtained by partially modifying the first embodiment.

As shown in FIG. 6, in the present embodiment, the piezoelectric film 40is etched in correspondence with the region where the upper-layermetallic film 50 is substantially formed. The alternating-currentvoltage applied to the upper-layer metallic film 50 is thus applied onlyin the vertically downward direction with no influence of the regionprovided with the lower-layer metallic film 30. Therefore prevented areundesired expansion and contraction motions of the piezoelectric film 40as well as transmission of an electrical signal. In the presentembodiment, after the step of dry etching the upper-layer metallic film50, dry etching is subsequently performed under the condition same asthat of the first embodiment with the residual resist film on theupper-layer metallic film 50 or the upper-layer metallic film 50 itselfserving as an etching mask. As a result, there is formed thepiezoelectric film 40 described above. Further, as shown in FIG. 6, thepiezoelectric film 40 is etched so as to be inclined (at an inclinationangle of 75°, for example) in the present embodiment. However, thepiezoelectric film 40 steeply inclined as shown in FIG. 6 is dealt inthe present application as being substantially visually unrecognized,with respect to other regions, in the front view of the ring-shapedvibrating gyroscope 400 shown in FIG. 6. Furthermore, the aspectdisclosed in the present embodiment in which the piezoelectric film 40is etched is applicable at least to all the embodiments of the presentapplication.

Modification (4) of First Embodiment

Described above in each of the first embodiment and the modifications(1) to (3) thereof is the configuration of the vibrating gyroscope thatis capable of detecting a biaxial angular velocity. Also obtained fromthe first embodiment is the disposition of respective detectionelectrodes for detecting a uniaxial angular velocity.

For example, when only the first detection electrodes 13 b, 13 c usedfor measuring an angular velocity with respect to the X axis, out of thefirst and second detection electrodes 13 b, 13 c, 13 d, 13 e, aredisposed on the ring-shaped vibrating body 11, manufactured is avibrating gyroscope for detection of a uniaxial angular velocity. Morespecifically, it is possible to obtain the vibrating gyroscope fordetection of a uniaxial angular velocity by selecting the detectionelectrodes for one axis out of the first detection electrodes and thesecond detection electrodes. As described earlier, the effect of thepresent invention is substantially exerted by disposing only one of thefirst detection electrodes (13 b, for example) out of the respectivefirst detection electrodes 13 b, 13 c.

Second Embodiment

FIG. 7 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope 500 according to the present embodiment.FIG. 8 is a cross sectional view taken along line B-B of FIG. 7.

As shown in FIGS. 7 and 8, the ring-shaped vibrating gyroscope 500according to the present embodiment includes a plurality of electrodes13 a to 13 f, similarly to the ring-shaped vibrating gyroscope 100 ofthe first embodiment. In the present embodiment, all the electrodes aredisposed outside or inside the center line.

In the present embodiment, excited to the ring-shaped vibratinggyroscope 500 is a primary vibration in an out-of-plane vibration modeof cos 3θ as indicated in FIG. 12A. On the other hand, a secondaryvibration in the present embodiment has an in-plane vibration mode ofcos 2θ. Accordingly, the plurality of electrodes 13 a to 13 f arecategorized as follows. Firstly, there are three driving electrodes 13a, 13 a, 13 a disposed 120° apart from each other in the circumferentialdirection. In a case where one of the above three driving electrodes 13a, 13 a, 13 a (for example, the driving electrode 13 a disposed in thedirection of twelve o'clock in FIG. 9) is set as a reference electrode,three monitor electrodes 13 f, 13 f, 13 f are disposed 60°, 180°, and300° respectively apart from the reference electrode 13 a in thecircumferential direction. Assume that the plane provided with apiezoelectric element on the ring-shaped vibrating body 11, in otherwords, the drawing sheet of FIG. 9, is referred to as an X-Y plane asindicated therein. In this case, the first detection electrodes 13 b, 13c for detecting an angular velocity about the X axis are disposed 0′,90°, 180°, and 270° respectively apart from the reference electrode inthe circumferential direction. Similarly, the second detectionelectrodes 13 d, 13 e for detecting an angular velocity about the Y axisare disposed 45°, 135°, 225°, and 315° respectively apart from thereference electrode in the circumferential direction.

The effect of the present invention is substantially exerted even withthe disposition of the respective detection electrodes. That is,provision of the respective detection electrodes 13 b, 13 c, 13 d, 13 eachieves detection of an angular velocity by adopting the biaxialin-plane vibration mode of cos 2θ. More specifically, FIG. 12B indicatesthe in-plane vibration mode of cos 2θ with respect to the X axis, whileFIG. 12C indicates the in-plane vibration mode of cos 2θ with respect tothe Y axis.

In the present invention, the driving electrodes 13 a, 13 a are disposedin a region from the outer peripheral edge of the ring-shaped vibratingbody 11 to a vicinity of the outer peripheral edge. However, the presentinvention is not limited to such a case. The respective drivingelectrodes 13 a are preferably disposed so as to excite only the primaryvibration in the out-of-plane vibration mode as well as to be unlikelyto excite the secondary vibration in the in-plane vibration mode. Suchdisposition is preferable because generation of the secondary vibrationwith no angular velocity being applied causes the ring-shaped vibratinggyroscope 500 to generate a zero point output. In the in-plane vibrationmode, it is a preferable aspect to dispose the respective drivingelectrodes 13 a so as to include the center line as each of the drivingelectrodes is less deformed in a vicinity of the center line, which isunlikely to excite the secondary vibration in the in-plane vibrationmode. In the in-plane vibration mode, the driving electrodes aredeformed in directions opposite to each other with respect to the centerline, it is a more preferable aspect to dispose the respective drivingelectrodes 13 a so as to be symmetrical with respect to the center line.

Modification of Second Embodiment

FIG. 9 is a front view of a structure having a principal function in aring-shaped vibrating gyroscope 600 obtained by partially modifying thefirst embodiment. FIG. 10 is a cross sectional view taken along line C-Cof FIG. 9.

In comparison to the second embodiment, the ring-shaped vibratinggyroscope 600 in the present embodiment is provided with a fixed end 60around the ring-shaped vibrating body 11 by way of grooves or legportions 17. Formed on the leg portions 17 and the fixed end 60 areelectrode pads 18 and the metal tracks 14 that are drawn from thedriving electrodes 13 a, 13 a, 13 a and the monitor electrodes 13 f, 13f, 13 f. Further, due to provision of the metal tracks 14 on the legportions 17, there are not provided the metal tracks 14 and theelectrode pads 18 on the leg portions 15 and the fixed end 19,respectively. In the present embodiment, eight leg portions 15 areremoved out of the sixteen leg portions 15 provided in the ring-shapedvibrating gyroscope 500 of the second embodiment. The ring-shapedvibrating gyroscope 600 in the present embodiment is configuredidentically with that of the second embodiment except for the abovepoints. The manufacturing method therefor is identical with that of thefirst embodiment except for some steps. The vibration modes of theprimary vibration and the secondary vibration in the present embodimentare identical with those of the second embodiment. Accordingly, thedescription duplicating with that of the first embodiment will not berepeatedly provided. Alternating-current power supplies to be connectedwith the driving electrodes 13 a, 13 a, 13 a are not illustrated in thepresent embodiment for easier comprehension of the figure.

Provision of the leg portions 17 in the present embodiment requires nocomplex wiring on the ring-shaped vibrating body 11. Thus remarkablydecreased are risks of short circuiting among the metal tracks by somedefect in the manufacturing steps. As shown in FIG. 9, each of the metaltracks 14 is joined to the center portion in the longer side of thecorresponding electrode, so that there are caused no variations inelectrical signals. Furthermore, because of expanded distances betweenthe respective leg portions 15, 17, expected are improvement inthroughput by increase in etching rate as well as improvement in yieldin the etching process in the manufacturing steps. However, provision ofthe fixed end 60 increases the size of the vibrating gyroscope incomparison to that of the first embodiment.

Each of the embodiments described above refers to the vibratinggyroscope using the ring-shaped vibrating body. However, the ring-shapedvibrating body may be replaced with a polygonal vibrating body. There isexerted an effect substantially similar to that of the present inventioneven with use of a vibrating body in a regular polygonal shape such as aregular hexagonal shape, a regular octagonal shape, a regulardodecagonal shape, a regular icosagonal shape, or the like. Furtheralternatively, there may be adopted a vibrating body such as adodecagonal vibrating body 111 of a ring-shaped vibrating gyroscope 700shown in FIG. 13. It is preferable, in view of stability of thevibrating body during the vibration motion, to adopt a vibrating body ina polygonal shape that is symmetrical with respect to a point in a frontview of the vibrating body. It is noted that the “ring shape” isinclusive of an elliptical shape. Unlike FIG. 1 and the like, the legportions and the post are not illustrated in FIG. 13 for easiercomprehension of the figure.

In each of the first embodiment and the modifications (1) to (3)thereof, the monitor electrodes 13 f, 13 f are disposed at the identicalpositions or in the identical regions. However, the present invention isnot limited to such a case. When N is a natural number of 2 or more or anatural number of 3 or more and M=0, 1, . . . , N−1 (hereinafter, alwaystrue in this paragraph), in a case where one of the driving electrodes13 a is set as a reference driving electrode, the monitor electrodes 13f are not necessarily disposed [(360/N)×{M+(½)}]° apart from thereference driving electrode 13 a in the circumferential direction. Forexample, in a vibration mode of cos Nθ, in a case where L=0, 1, . . . ,2N−1(hereinafter, always true in this paragraph), when the monitorelectrodes 13 f are disposed so as not to be [(180/N)×{L+(½)}]° apartfrom the reference driving electrode in the circumferential direction orare disposed so as not to be axisymmetrical with respect to the aboveangular positions, the effect of the first embodiment or a modificationthereof is substantially exerted. In a limited planar region of thering-shaped vibrating body 11 that is particularly reduced in size, thedisposition of the monitor electrodes 13 f as in the first embodimentwill facilitate the disposition of the other electrode groups and/or themetal tracks. More specifically, when N is a natural number of 2 or moreor a natural number of 3 or more and M=0, 1, . . . , N−1 (hereinafter,always true in this paragraph), in a case where one of the drivingelectrodes 13 a is set as a reference driving electrode, it is apreferable aspect to dispose the monitor electrodes 13 f so as to be[(360/N)×{M+(½)}]° apart from the reference driving electrode 13 a inthe circumferential direction.

One specific example of the above is a ring-shaped vibrating gyroscope800 shown in FIG. 14A. When N is a natural number of 2 or more or anatural number of 3 or more and M=0, 1, . . . , N−1 (hereinafter, alwaystrue in this paragraph), in a case where one of the driving electrodes13 a is set as a reference driving electrode, monitor electrodes 213 f,213 f of the ring-shaped vibrating gyroscope 800 are not necessarilydisposed [(360/N)×{M+(½)}]° apart from the reference driving electrode13 a in the circumferential direction. However, an effect similar tothat of the first embodiment is exerted even with the disposition of themonitor electrodes 213 f, 213 f, 213 f, 213 f shown in FIG. 14A.

Another example of the above is a ring-shaped vibrating gyroscope 820shown in FIG. 14B. In the ring-shaped vibrating gyroscope 820, monitorelectrodes 313 f, 313 f are disposed as if two out of the monitorelectrodes 213 f, 213 f, 213 f, 213 f are removed from the ring-shapedvibrating gyroscope 800 shown in FIG. 14A. However, an effect similar tothat of the first embodiment is exerted even with the disposition of themonitor electrodes 313 f, 313 f shown in FIG. 14B.

Still another example of the above is a ring-shaped vibrating gyroscope840 shown in FIG. 14C. In the ring-shaped vibrating gyroscope 840,monitor electrodes 413 f, 413 f are disposed as if the remaining two outof the monitor electrodes 213 f, 213 f, 213 f, 213 f are removed fromthe ring-shaped vibrating gyroscope 800 shown in FIG. 14A. However, aneffect similar to that of the first embodiment is exerted even with thedisposition of the monitor electrodes 313 f, 313 f shown in FIG. 14C.

Further, a different example of the above is a ring-shaped vibratinggyroscope 860 shown in FIG. 14D. In the ring-shaped vibrating gyroscope860, monitor electrodes 513 f, 513 f are disposed as if two differentfrom the above cases out of the monitor electrodes 213 f, 213 f, 213 f,213 f are removed from the ring-shaped vibrating gyroscope 800 shown inFIG. 14A. However, an effect similar to that of the first embodiment isexerted even with the disposition of the monitor electrodes 513 f, 513 fshown in FIG. 14D.

Moreover, a different example of the above is a ring-shaped vibratinggyroscope 880 shown in FIG. 14E. Some of monitor electrodes 613 f, 613f, 613 f, 613 f of the ring-shaped vibrating gyroscope 880 are disposedin a region from the inner peripheral edge to the center line of thering-shaped vibrating body 11. Each of second detection electrodes 13 d,13 e has a smaller area. However, an effect similar to that of the firstembodiment is exerted even with the disposition of the monitorelectrodes 613 f, 613 f. 613 f, 613 f, shown in FIG. 14E, except thatthe sensitivity of each of the detection electrodes is deteriorated toresult in decrease in ratio of S (signal) and N (noise) (what is calledan S/N ratio). Similarly, even in a case where some or all of themonitor electrodes 613 f, 613 f, 613 f, 613 f are disposed in a regionfrom the outer peripheral edge to the center line of the ring-shapedvibrating body 11, an effect similar to that of the first embodiment isexerted.

The above technical idea on the disposition of the monitor electrodes 13f is applicable to the second embodiment described above. Morespecifically, for example, an effect of the second embodiment issubstantially exerted by disposing each of the monitor electrodes so asnot to be 30° apart from the corresponding driving electrode, likemonitor electrodes 713 f, 713 f, 713 f, 713 f of a ring-shaped vibratinggyroscope 900 shown in FIG. 14F.

As shown in each of the examples described above, in any one of thering-shaped vibrating gyroscopes according to the present invention,excited is the primary vibration in the out-of-plane vibration mode.Thus, the monitor electrodes may be disposed on the plane of thering-shaped vibrating body 11 with a high degree of flexibility as longas being in a region from the inner peripheral edge to the outerperipheral edge thereof. However, for example, in a vibration mode ofcos Nθ, when L=0, 1, . . . , 2N−1 (hereinafter, always true in thisparagraph), the respective monitor electrodes 13 f are disposed so asnot to be [(180/N)×{L+(½)}]° apart from the reference driving electrodein the circumferential direction or are disposed so as not to beaxisymmetrical with respect to the above angular positions. The monitorelectrodes are not disposed at such former positions since deformationof the ring-shaped vibrating body 11 is eliminated (zero) at the formerpositions. The monitor electrodes are not disposed at such latterpositions since the electrodes are deformed in directions opposite toeach other so as to cancel the deformations each other. In a limitedplanar region of the ring-shaped vibrating body 11 that is particularlyreduced in size, the disposition of the monitor electrodes 13 f as inthe first embodiment will facilitate the disposition of the otherelectrode groups and/or the metal tracks. More specifically, when N is anatural number of 2 or more or a natural number of 3 or more and M=0, 1,. . . , N−1 (hereinafter, always true in this paragraph), in a casewhere one of the driving electrodes 13 a is set as a reference drivingelectrode, it is a preferable aspect to dispose the monitor electrodes13 f so as to be [(360/N)×{M+(½)}]° apart from the reference drivingelectrode 13 a in the circumferential direction.

Moreover, adopted in each of the embodiments described above is thering-shaped vibrating gyroscope that is mainly made of silicon. However,these embodiments are not limited to such a case. Alternatively, themain material for the vibrating gyroscope may be germanium or silicongermanium, for example. In the above examples, it is possible to applythe known anisotropic dry etching technique by particularly adoptingsilicon or silicon germanium, which results in significant contributionto the improvement in processing accuracy of the entire gyroscopeincluding the vibrating body. As having been described so far,modifications made within the scope of the present invention inclusiveof other combinations of the respective embodiments will be alsoincluded in the scope of the patent claims.

INDUSTRIAL APPLICABILITY

The present invention is applicable, as a vibrating gyroscope, toportions of various types of devices.

1. A vibrating gyroscope comprising: a ring-shaped vibrating body havinga uniform plane; a leg portion flexibly supporting the ring-shapedvibrating body and having a fixed end; a fixed potential electrode; anda plurality of electrodes formed on the plane with a piezoelectric filmsandwiched between an upper-layer metallic film and a lower-layermetallic film in a thickness direction thereof, wherein the plurality ofelectrodes include: (1) when N is a natural number of 2 or more, a groupof driving electrodes for exciting a primary vibration of thering-shaped vibrating body in a vibration mode of cos Nθ, which aredisposed (360/N)° apart from each other in a circumferential direction;and (2) a group of detection electrodes for detecting a secondaryvibration in a vibration mode of cos(N+1)θ generated when an angularvelocity is applied to the ring-shaped vibrating body, and, when one ofthe driving electrodes is set as a reference driving electrode and S=0,1, . . . , N (hereinafter true), the group of detection electrodeshaving an electrode disposed [{360/(N+1)}×S]° apart from the referencedriving electrode and/or an electrode disposed [{360/(N+1)}×{S+(½)}]°apart from the reference driving electrode, and each of the drivingelectrodes is disposed on a first electrode disposition portion in theplane, and each of the detection electrodes is disposed on a secondelectrode disposition portion that is not electrically connected to thefirst electrode disposition portion and has a region from an outerperipheral edge of the ring-shaped vibrating body to a vicinity of theouter peripheral edge and/or a region from an inner peripheral edgethereof to a vicinity of the inner peripheral edge.
 2. The vibratinggyroscope according to claim 1, wherein when the detection electrodesare referred to as first detection electrodes, the plurality ofelectrodes further include: (3) a group of second detection electrodesfor detecting a secondary vibration of a vibration axis {90/(N+1)}°apart from that of the secondary vibration in (2), and the group ofsecond detection electrodes having an electrode disposed[{360/(N+1)}×{S+(¼)}]° apart from the reference driving electrode and/oran electrode disposed [{360/(N+1)}×{S+(¾)}]° apart from the referencedriving electrode, and each of the second detection electrodes isdisposed on the second electrode disposition portion.
 3. The vibratinggyroscope according to claim 1, wherein the plurality of electrodesfurther include: (4) when M=0, 1, . . . , 2N−1 (hereinafter true), agroup of monitor electrodes disposed so as not to be (180/N)×{M+(½)}°apart from the reference driving electrode in the circumferentialdirection.
 4. The vibrating gyroscope according to claim 1, wherein theplurality of electrodes further include: (4) when one of the drivingelectrodes is set as a reference driving electrode and M=0, 1, . . . ,N−1 (hereinafter true), a group of monitor electrodes disposed(360/N)×{M+(½)}° apart from the reference driving electrode in thecircumferential direction.
 5. The vibrating gyroscope according to claim1, wherein the first electrode disposition portion includes a centerline connecting centers in a width direction from the outer peripheraledge to the inner peripheral edge.
 6. The vibrating gyroscope accordingto claim 1, wherein the ring-shaped vibrating body is formed with asilicon substrate, and only the upper-layer metallic film, thepiezoelectric film, and the lower-layer metallic film are substantiallyvisible in a front view.
 7. The vibrating gyroscope according to claim1, wherein the ring-shaped vibrating body is formed with a siliconsubstrate, and only the upper-layer metallic film and the lower-layermetallic film are substantially visible in a front view.
 8. A vibratinggyroscope comprising: a ring-shaped vibrating body having a uniformplane; a leg portion flexibly supporting the ring-shaped vibrating bodyand having a fixed end; a fixed potential electrode; and a plurality ofelectrodes formed on the plane with a piezoelectric film sandwichedbetween an upper-layer metallic film and a lower-layer metallic film ina thickness direction thereof, wherein the plurality of electrodesinclude: (1) when N is a natural number of 2 or more, a group of drivingelectrodes for exciting a primary vibration of the ring-shaped vibratingbody in a vibration mode of cos Nθ, which are disposed (360/N)° apartfrom each other in a circumferential direction; and (2) a group ofdetection electrodes for detecting a secondary vibration in a vibrationmode of cos(N+1)θ generated when an angular velocity is applied to thering-shaped vibrating body, and, when one of the driving electrodes isset as a reference driving electrode and S=0, 1, . . . , N (hereinaftertrue), the group of detection electrodes having an electrode disposed[{360/(N+1)}×{S+(¼)}]° apart from the reference driving electrode and/oran electrode disposed [{360/(N+1)}×{S+(¾)}]° apart from the referencedriving electrode, and each of the driving electrodes is disposed on afirst electrode disposition portion in the plane, and each of thedetection electrodes is disposed on a second electrode dispositionportion that is not electrically connected to the first electrodedisposition portion and has a region from an outer peripheral edge ofthe ring-shaped vibrating body to a vicinity of the outer peripheraledge and/or a region from an inner peripheral edge thereof to a vicinityof the inner peripheral edge.
 9. The vibrating gyroscope according toclaim 8, wherein the plurality of electrodes further include: (4) whenM=0, 1, . . . , 2N−1 (hereinafter true), a group of monitor electrodesdisposed so as not to be (180/N)×{M+(½)}° apart from the referencedriving electrode in the circumferential direction.
 10. The vibratinggyroscope according to claim 8, wherein the plurality of electrodesfurther include: (4) when one of the driving electrodes is set as areference driving electrode and M=0, 1, . . . , N−1 (hereinafter true),a group of monitor electrodes disposed (360/N)×{M+(½)}° apart from thereference driving electrode in the circumferential direction.
 11. Thevibrating gyroscope according to claim 8, wherein the first electrodedisposition portion includes a center line connecting centers in a widthdirection from the outer peripheral edge to the inner peripheral edge.12. The vibrating gyroscope according to claim 8, wherein thering-shaped vibrating body is formed with a silicon substrate, and onlythe upper-layer metallic film, the piezoelectric film, and thelower-layer metallic film are substantially visible in a front view. 13.The vibrating gyroscope according to claim 8, wherein the ring-shapedvibrating body is formed with a silicon substrate, and only theupper-layer metallic film and the lower-layer metallic film aresubstantially visible in a front view.
 14. A vibrating gyroscopecomprising: a ring-shaped vibrating body having a uniform plane; a legportion flexibly supporting the ring-shaped vibrating body and having afixed end; a fixed potential electrode; and a plurality of electrodesformed on the plane with a piezoelectric film sandwiched between anupper-layer metallic film and a lower-layer metallic film in a thicknessdirection thereof, wherein the plurality of electrodes include: (1) whenN is a natural number of 3 or more, a group of driving electrodes forexciting a primary vibration of the ring-shaped vibrating body in avibration mode of cos Nθ, which are disposed (360/N)° apart from eachother in a circumferential direction; and (2) a group of detectionelectrodes for detecting a secondary vibration in a vibration mode ofcos(N−1)θ generated when an angular velocity is applied to thering-shaped vibrating body, and, when one of the driving electrodes isset as a reference driving electrode and S=0, 1, . . . , N−2(hereinafter true), the group of detection electrodes having anelectrode disposed [{360/(N−1)}×S]° apart from the reference drivingelectrode and/or an electrode disposed [{360/(N−1)}×{S+(½)}]° apart fromthe reference driving electrode, and each of the driving electrodes isdisposed on a first electrode disposition portion in the plane, and eachof the detection electrodes is disposed on a second electrodedisposition portion that is not electrically connected to the firstelectrode disposition portion and has a region from an outer peripheraledge of the ring-shaped vibrating body to a vicinity of the outerperipheral edge and/or a region from an inner peripheral edge thereof toa vicinity of the inner peripheral edge.
 15. The vibrating gyroscopeaccording to claim 14, wherein when the detection electrodes arereferred to as first detection electrodes, the plurality of electrodesfurther include: (3) a group of second detection electrodes fordetecting a secondary vibration of a vibration axis {90/(N−1)}° apartfrom that of the secondary vibration in (2), and the group of seconddetection electrodes having an electrode disposed [{360/(N−1)}×{S+(¼)}]°apart from the reference driving electrode and/or an electrode disposed[{360/(N−1)}×{S+(¾)}]° apart from the reference driving electrode, andeach of the second detection electrodes is disposed on the secondelectrode disposition portion.
 16. The vibrating gyroscope according toclaim 14, wherein the plurality of electrodes further include: (4) whenM=0, 1, . . . , 2N−1 (hereinafter true), a group of monitor electrodesdisposed so as not to be (180/N)×{M+(½)}° apart from the referencedriving electrode in the circumferential direction.
 17. The vibratinggyroscope according to claim 14, wherein the plurality of electrodesfurther include: (4) when one of the driving electrodes is set as areference driving electrode and M=0, 1, . . . , N−1 (hereinafter true),a group of monitor electrodes disposed (360/N)×{M+(½)}° apart from thereference driving electrode in the circumferential direction.
 18. Thevibrating gyroscope according to claim 14, wherein the first electrodedisposition portion includes a center line connecting centers in a widthdirection from the outer peripheral edge to the inner peripheral edge.19. The vibrating gyroscope according to claim 14, wherein thering-shaped vibrating body is formed with a silicon substrate, and onlythe upper-layer metallic film, the piezoelectric film, and thelower-layer metallic film are substantially visible in a front view. 20.The vibrating gyroscope according to claim 14, wherein the ring-shapedvibrating body is formed with a silicon substrate, and only theupper-layer metallic film and the lower-layer metallic film aresubstantially visible in a front view.
 21. A vibrating gyroscopecomprising: a ring-shaped vibrating body having a uniform plane; a legportion flexibly supporting the ring-shaped vibrating body and having afixed end; a fixed potential electrode; and a plurality of electrodesformed on the plane with a piezoelectric film sandwiched between anupper-layer metallic film and a lower-layer metallic film in a thicknessdirection thereof, wherein the plurality of electrodes include: (1) whenN is a natural number of 3 or more, a group of driving electrodes forexciting a primary vibration of the ring-shaped vibrating body in avibration mode of cos Nθ, which are disposed (360/N)° apart from eachother in a circumferential direction; and (2) a group of detectionelectrodes for detecting a secondary vibration in a vibration mode ofcos(N−1)θ generated when an angular velocity is applied to thering-shaped vibrating body, and, when one of the driving electrodes isset as a reference driving electrode and S=0, 1, . . . , N−2(hereinafter true), the group of detection electrodes having anelectrode disposed [{360/(N−1)}×{S+(¼)}]° apart from the referencedriving electrode and/or an electrode disposed [{360/(N−1)}×{S+(¾)}]°apart from the reference driving electrode, and each of the drivingelectrodes is disposed on a first electrode disposition portion in theplane, and each of the detection electrodes is disposed on a secondelectrode disposition portion that is not electrically connected to thefirst electrode disposition portion and has a region from an outerperipheral edge of the ring-shaped vibrating body to a vicinity of theouter peripheral edge and/or a region from an inner peripheral edgethereof to a vicinity of the inner peripheral edge.
 22. The vibratinggyroscope according to claim 21, wherein the plurality of electrodesfurther include: (4) when M=0, 1, . . . , 2N−1 (hereinafter true), agroup of monitor electrodes disposed so as not to be (180/N)×{M+(½)}°apart from the reference driving electrode in the circumferentialdirection.
 23. The vibrating gyroscope according to claim 21, whereinthe plurality of electrodes further include: (4) when one of the drivingelectrodes is set as a reference driving electrode and M=0, 1, . . . ,N−1 (hereinafter true), a group of monitor electrodes disposed(360/N)×{M+(½)}° apart from the reference driving electrode in thecircumferential direction.
 24. The vibrating gyroscope according toclaim 21, wherein the first electrode disposition portion includes acenter line connecting centers in a width direction from the outerperipheral edge to the inner peripheral edge.
 25. The vibratinggyroscope according to claim 21, wherein the ring-shaped vibrating bodyis formed with a silicon substrate, and only the upper-layer metallicfilm, the piezoelectric film, and the lower-layer metallic film aresubstantially visible in a front view.
 26. The vibrating gyroscopeaccording to claim 21, wherein the ring-shaped vibrating body is formedwith a silicon substrate, and only the upper-layer metallic film and thelower-layer metallic film are substantially visible in a front view.